Air Quality Index (AQI) forecasts and current conditions (for USA) are available in Keyhole Markup Language (KML) format at the EPA website. Download and open this data layer in Google Earth.

Terradex publishes a realtime air quality monitoring layer displayed on Google Earth as well. The service was recently awarded an Environmental Achievement Award by the United States Environmental Protection Agency. This layer covers the USA, UK and Hongkong, China and Mexico. Find out more from Google Lat Long Blog.